This application pertains to the art of optics and more particularly to optical lenses.
The invention is particularly applicable to a lens blank processing method and apparatus for eyeglass lenses and will be described with particular reference thereto. However, it will be appreciated by those skilled in the art that the invention has broader applications and may be adapted for practical use in processing other types of optical lenses employed in various environments.
In processing lens blanks into finished optical lenses for eyeglasses, many types of processing methods and apparatus have heretofore been employed. To some extent, the exact method steps and types of apparatus utilized have been dictated by the specifics of the lens generating, polishing and edging equipment utilized. Most processing methods have, however, required measuring of the lens blank for purposes of locating a desired optical center axis as prescribed by the lens prescription for allowing subsequent mounting of a lens block to the blank at that axis. The lens block facilitates convenient lens blank mounting in lens surface generating apparatus in order that the concave lens blank surface may be ground to a desired prescription. Following generation, the lens blank is fined and polished and then edged in separate processing apparatus. Typically, in order to achieve the final lens characteristics suitable for eyeglass use, it has been necessary to deblock and reblock the lens blank at least once during the fining and polishing and edging operations in order that the blank may be properly positioned relative to the processing apparatus involved. In addition, standard lens blocks often have diameters greater than the edged size of the lens. Such a dimensional relationship necessitates reblocking of lens blanks for edging purposes.
Heretofore, there have been quite a number of types and styles of lens blocks or lens blocking means for accommodating lens blank mounting in particular processing apparatus. These prior lens blocking arrangements are somewhat complex and do not effectively eliminate the necessity for lens blank layout prior to lens block mounting. Some of these prior lens blocking structures have essentially been comprised of two lens block components wherein one component is utilized in mounting the lens blank for some processing operations and the other component is utilized for mounting the lens blank in other processing operations. Usually, the first of these components must be removed from its blocked position on the lens blank prior to using the second component for subsequent processing operations. Moreover, some prior lens block arrangements have been configured so as to cover substantially the entire lens blank surface to which they are affixed. Thus, during lens blank edging, the lens block is itself partially consumed and is not reusable for processing additional lens blanks.
More particularly, one type of commonly used process for generating optical lenses from lens blanks entails mounting a lens block to the convex surface of the lens blank by means of a molten alloy so that the longitudinal axis of the lens block is substantially coaxial with the desired optical center axis of the lens blank. In such mounting, it is necessary to first lay out the lens blank by special layout apparatus to physically locate the optical center axis and any necessary rotation of the lens blank base line commensurate with the lens prescription. Thereafter, the lens block is mounted to the lens blank by the molten alloy with the block located on the convex lens blank surface at the optical center axis. At such mounting, the lens block is also rotated for accommodating any axis characteristics which are to be imparted to the lens in accordance with the prescription. The lens blank and lens block are then mounted in the lens surface generating apparatus which grinds the concave lens blank surface to prescription. When it is desired to impart prism characteristics to the lens blank, the lens block is often shimmed in the lens surface generating apparatus to angularly offset the lens blank optical center axis from its normal position.
Following surface generation, the lens blank and associated lens block are mounted in fining and polishing apparatus in order that the ground surface may be polished to the requisite optical quality. Thereafter, the partially completed lens blank is deblocked from the lens block and laid out a second time for properly locating a lens block which will accommodate edging apparatus. The lens blank is then reblocked, installed in edging apparatus and the lens blank edge ground to secure the final peripheral edge configuration. Following edging, the final lens is deblocked for any final processing steps and ultimately installation into the eyeglass frame.
The above described commonly used processing arrangement requires a substantial amount of hand labor and time for achieving lens blank layout and blocking. This labor and time is increased due to the fact that two separate layout and blocking steps are employed during processing of each lens. In addition, the fact that both the initial lens blank and partially processed lens blank require layout necessitate provision of special layout tools and operator skill. These factors, as well as others noted hereinabove, necessarily add to the cost and overall production time required for each lens.
It has, therefore, been desired to develop means whereby the various problems encountered in prior processing methods and apparatus could be overcome in order to increase the overall efficiency and reliability of lens production. The subject invention contemplates new and improved method and apparatus which meet these needs and provides a lens processing method and apparatus which are simple, require only a single blocking of the lens blank during the entire processing thereof into a finished lens, economical to use, which are useful in generating substantially all types of single and multivision lens prescriptions and which are adaptable to application in other environments.